Parts and materials may be moved in a manufacturing environment by roller conveyors that have many rollers to support the parts and materials, and/or to support a tray or pallet that holds the parts and materials. Conventional roller conveyors typically have many idle and driven rollers disposed between guide rails along which the parts and materials are moved.
Roller conveyors that operate in clean room manufacturing environments must satisfy certain requirements that may not be important in other industrial environments. For example, it may be desired for a roller conveyor in a clean room manufacturing environment to be designed to operate in such a way that certain debris-generating occurrences are prevented or reduced. Such debris-generating occurrences may include collisions between upstream and downstream parts, materials, trays, or pallets. Such collisions may cause an amount of debris that would be unacceptable in many clean room environments. Also, an unacceptable amount of debris may be generated if a drive roller is forced to rotate and rub against a part or tray that has been impeded from traveling along the conveyor at the speed that would otherwise have been compelled by the drive roller.
Clean room roller conveyors have been disclosed in the art to prevent or reduce such debris-generating occurrences. For example, so-called “zone controlled” conveyors have multiple sensors and drive rollers that are driven independently or in groups. The drive rollers may be independently driven in response to the sensor output, so that the conveyor will not attempt to propel an upstream part or tray into a downstream zone unless that downstream zone is free to accept the upstream part or tray without collision or obstruction. Hence, through the use of several independently controlled motors driving rollers in various zones of the conveyor, debris-generating occurrences may be reduced in the clean room manufacturing environment.
FIG. 1 is a perspective view of a contemporary zone-controlled clean room conveyor 100. The clean room conveyor 100 includes a plurality of drive rollers 102 and a plurality of idle rollers 112 disposed between a first guide rail 120 and a second guide rail 130. The first guide rail 120 includes a plurality of independently controllable motors 122, each driving a drive roller 102. The second guide rail 130 supports the plurality of idle rollers 112, which are not driven by any motor. Each of the drive rollers 102 is opposite one of the idle rollers 112, so that the moving part or pallet encounters successive pairs of rollers, each pair including one drive roller 102 and one idle roller 112. The contemporary zone-controlled clean room conveyor may be divided into zones, each zone comprising a sub-group of the plurality of independently controllable motors 122.
FIG. 2 is a top view of the contemporary clean room conveyor 100. The first guide rail 120 of the contemporary zone-controlled clean room conveyor 100 is wider than the second guide rail 130, because the first guide rail 120 includes the plurality of independently controllable motors 122, while the second guide rail 130 does not include any motors. The minimum width of the contemporary zone-controlled clean room conveyor 100 includes the width of the first and second guide rails 120, 130 themselves, plus the minimum spacing between the first and second guide rails that is required to accommodate the parts, material, trays, and/or pallets that must be moved by the conveyor 100.
Due to the equipment and procedures required to keep a clean room environment acceptably clean during manufacturing operations, clean room facilities are more expensive than industrial, manufacturing, and assembly space outside of the clean room facilities. Therefore, space within clean room facilities is generally limited, and there is a need in the art for a clean room conveyor having a reduced width, for example to make room for other conveyors, equipment, tools, work space, or supplies within the clean room facilities.